In the oil and gas exploration and extraction industry, well bores are lined with metal tubing. Typically, the majority of a well will be lined with tubing known as casing, while the distal end of the well is provided with smaller diameter tubing known as liner. Generally, the section of the well provided with the liner will intersect the hydrocarbon-bearing formation. The liner may be suspended from the lower end of the casing by means of a liner hanger.
Conventionally, the liner hanger is a tubular assembly which is mounted on the upper end of the liner. The hanger is run into the casing with the liner and then configured first to engage and then to seal with the casing inner surface.
There is an undesirable loss of liner internal diameter associated with the provision of conventional liner hangers, and this is one reason behind the development of alternative hanger arrangements, such as proposed in WO99\18328 (Bailey et al). The disclosed hanger arrangement is achieved by expanding the upper end of the liner within a larger diameter casing, with a tubular spacer located therebetween. The liner, casing and spacer are of similar material. The liner is expanded past its yield point sufficiently to expand the spacer and the casing, with the intention that, following release of the expansion force, the elastic recovery of the liner is less than the elastic recovery for the casing. It is suggested that this provides for interference between the expanded liner, spacer and casing, sufficient to provide the necessary hanging support for the liner.
It is among the objectives of embodiments of the invention to provide a method and apparatus for use in forming a liner hanger which will provide a secure and reliable coupling between the liner and casing.